A week after this largely peaceful sit-in in New York City’s financial district began, the Occupy Wall Street protest turned violent on Saturday when demonstrators clashed with cops, leading to dozens of arrests.

Corralled by orange police nets, protesters marched uptown to Union Square, chanting their calls for change while staying within the barriers the police had set. But push turned to shove, and a protest turned to a clash in what seems like a moment.

A couple of on-the-scene videos show officers reacting harshly to the protesters when they refused to step back on the sidewalk. While police held up a net to keep them contained, cameras caught an NYPD officer – in a white shirt, which indicates a rank of lieutenant or above – walking toward the barrier and spraying pepper spray on the demonstrators.

The video above, originally posted on USLaw.com, shows a slowed-down version of events with annotations. The split-second video barely catches the action, but those who were hit by the spray spoke out later. A cop “just comes along and does these quick little spritzes of pepper spray in my and these three other girls’ eyes,” Chelsea Elliott, 25, told the New York Times. The girls, temporarily blinded by the stinging spray, fell to the ground in tears.

NYPD chief spokesman Paul J. Browne told the Times that police had used the pepper spray “appropriately.” But protest spokesman Patrick Bruner called the police response “exceedingly violent,” maintaining that demonstrators sought to remain peaceful. The NYPD reports that about 80 people were arrested, primarily for disorderly conduct and blocking traffic.

The protest, in its second week, started as a largely online effort to get people to speak out against financial greed and corruption. The event has seen sparse attendance, with demonstrators unable to agree on a specific target: some have railed against corporations, others targeting taxes, and some bashing Washington in general. Their numbers have not stacked up to the 20,000 people organizers had hoped to see.

Nick Carbone is a reporter at TIME. Find him on Twitter at @nickcarbone. You can also continue the discussion on TIME’s Facebook page and on Twitter at @TIME.